Hi mama! Honestly, I'd suggest getting that checked with your pediatrician agad lang, even kung maliit lang siya, it's better to have a doctor look at it para sure, kasi mahirap judgment lang from pictures or descriptions. One of my mum friends had something similar sa baby niya and turned out it was just a harmless cyst, pero relief lang talaga na confirmed ng doctor, so please don't worry pero have it checked na lang soon para peace of mind mo.